General Musical Instruments
A musical instrument is a device that is able to generate musical vibrations and launch them into the air. Each instrument sound is characteristically different according to its tone color or timbre; that is, a combination of a fundamental vibrational mode and a number of harmonics, or overtones, of varying amplitudes which uniquely distinguish its sound from the sounds of other instruments. Instrument sounds are also characterized by pitch (determined by the rate of vibration); the duration of the vibration, and the dynamic range of the instrument as determined by the force of the vibration.
Musical instrument sounds are generated in various ways including the setting into motion of one or more strings mounted on the instrument body; an instrument body or stretched membrane set into vibration by external percussion; or the blowing of air through a series of air columns, cavities, channels or reeds. These vibrations are transmitted from the instrument through the air and are received by the human ear at an intensity determined by the distance between the instrument and the receiver.
In instances where an amplification of the instrument sound is required, an audio microphone can be placed in close proximity to the instrument body to pickup the vibrations and electrically transmit the sounds to an amplification system. In some instances, it is desired to isolate the instrument from its immediate surrounding and provide single channel amplification through the use of a contact microphone, or acoustic transducer, which is affixed directly to the instrument to pick up the vibrations in the body.